CVE-2019-20832 in PhantomPDF
Summary
by MITRE
An issue was discovered in Foxit PhantomPDF before 8.3.10. It has homograph mishandling.
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Analysis
by VulDB Data Team • 10/22/2020
The vulnerability identified as CVE-2019-20832 represents a significant security flaw in Foxit PhantomPDF software versions prior to 8.3.10, specifically concerning homograph mishandling. This issue falls under the broader category of internationalized domain names and character encoding vulnerabilities that have become increasingly prevalent in modern software applications. Homograph attacks exploit the visual similarity of different character sets to deceive users into believing they are interacting with legitimate systems while actually encountering malicious ones. The flaw manifests when the PDF reader fails to properly distinguish between visually similar characters from different Unicode scripts, creating opportunities for attackers to craft deceptive file names or URLs that appear authentic but contain malicious elements.
The technical implementation of this vulnerability stems from insufficient validation of Unicode characters during the parsing and display of PDF documents. When processing documents containing characters from multiple scripts such as Latin, Cyrillic, or Arabic, the software does not adequately enforce character set boundaries or perform proper normalization checks. This weakness allows attackers to embed homograph characters that visually resemble legitimate file extensions or domain names, potentially leading to phishing attacks or malicious file execution. The vulnerability directly relates to CWE-1004 which addresses insecure default permissions and improper handling of internationalized characters, and aligns with ATT&CK technique T1059.001 for command and scripting interpreter usage in phishing contexts.
The operational impact of this vulnerability extends beyond simple document viewing, as it creates potential attack vectors for social engineering campaigns targeting users of the affected software. An attacker could craft a PDF document with a filename that appears to be a legitimate document such as "report.pdf" while actually containing characters that visually resemble the original but are from a different Unicode script. This could lead to users inadvertently executing malicious code or navigating to phishing sites when clicking on what appears to be a safe document. The vulnerability is particularly concerning in enterprise environments where users frequently interact with PDF documents from external sources and may not be adequately trained to recognize such subtle visual deception techniques.
Organizations utilizing Foxit PhantomPDF software should immediately upgrade to version 8.3.10 or later to remediate this vulnerability. Additionally, administrators should implement enhanced monitoring for suspicious file naming patterns and consider deploying network-based solutions that can detect and block homograph-based attacks. Security awareness training should emphasize the importance of verifying file authenticity through multiple means beyond visual inspection, particularly when dealing with documents from untrusted sources. The mitigation strategy should also include regular security assessments of document handling processes and implementation of proper input validation controls that enforce character set restrictions for file names and URLs within the PDF processing environment.